Failure to assure sustainable food security will foster the very conditions that will further destabilize and polarize the world in the years to come, with tremendous consequences for all people. This lecture discusses six kinds of action required for global food needs to be met without damage to the environment: selective strengthening of the capacity of developing-country governments; investing more in poor people; accelerating agricultural productivity; assuring sound management of natural resources; developing competitive markets; and expanding and realigning international development assistance. Projections of the incidence of malnutrition population growth, cereal supply and demand, cereal prices, and advances in food production underscore the seriousness of potential threats to food security and the environment. To illustrate the opportunities associated with alternative actions to mitigate threats to sustainable food security, the authors demonstrate how numbers of malnourished children would be affected under two scenarios, a pessimistic scenario (slow income growth and low investment in national and international agricultural research) and an optimistic scenario (rapid income growth and higher investment in national and international agricultural research, as well as investment in public goods such as health and education).20 pages